Pre-Workout Protein Boosts Metabolism

We were recently on the topic of fasted training and the need for pre-workout protein intake as a slight compromise to training completely fasted.

I argued that the need for pre-workout protein intake was due to this being a case where the benefits (increased protein synthesis) simply outweighted the negatives (insulin increase; low insulin being a determinant of the fasting state). It’s also known that BCAAs independently affects the same myogenic pathway through which fasted training may increase protein synthesis in response to post-workout nutrition.

On the whole, the scientific evidence that speaks in favor of pre-workout protein for increased protein synthesis and muscle growth is strong. Some researchers even speculate that it may be just as important as post-workout protein intake.

Last week I came across another study which makes a strong argument for pre-workout protein to facilitate body fat loss. Let me give you a brief summary of the findings.

Participants were recruited for two experiments where they ingested 18-19 g whey protein or carbs 20 min pre-workout. It should be noted that they all had weight-training experience; they were not newbies. Resting energy expenditure (REE) was measured on the morning before training and at the 24- and 48-hour marks post-workout. Respiratory Exchange Ratio (RER) was also measured at these time points; in short, RER is a way to quantify the ratio of fat, carb and protein oxidation at rest.

The training was in the form of a full-body session, with nine different movements trained 4 x 10-12, with a 2 min rest between sets. Bench press, squats and sit ups were some of the movements of choice.

Results showed that REE was significantly elevated at the 24-hour mark when compared to baseline.

Using a typical 80 kg/176 lbs male as an example, here’s what the experiments showed

Baseline (before training): 1730 kcal

24 hours post-workout (carbs): 1790 kcal (+3.5% vs baseline)

24 hours post-workout (protein): 1880 kcal (+8.5% vs baseline)

48 hours post-workout: at this point, no clinically significant differences where seen between carbs and protein, but REE was still elevated approximately 6-6.5% above baseline in both experiments.

It’s interesting to note that the carb-supplemented experiment caught up with the protein-supplemented experiment in terms of REE at the 48-hour mark, while lagging behind big time at the 24 hour mark. The difference of 90 kcal between carb and protein-supplemented experiments can be seen as fairly substantial in this context. It’s more than what many thermogenic supplements would yield. The degree of latency is also interesting. One would hardly think that your pre-workout nutrient intake would affect protein synthesis 24 hours later.

REE was tilted towards increased fat burning at the 24-hour mark, but this effect was not affected by pre-workout nutrition. In this case there were no differences between protein or carbs.

Why does pre-workout protein boost metabolic rate when carbs doesn’t?

The higher REE observed in the protein-supplemented experiment can be explained by increased muscle protein synthesis, which is a metabolically costly process. Older studies show that consuming pre-workout protein increase protein synthesis far more effectively than pre-workout carbs. This effect is due to shuttling amino acids to the working muscles, which in turn may increases protein synthesis for up to 48 hours. It goes without saying that if no dietary amino acids are present at this time, the effect would be blunted, which is what occurs if one would work out completely fasted or with carbs only.

The researchers put forth another hypothesis for the increased REE seen in the protein supplemented group. Pre-workout protein blunts cortisol throughout the day, which is another effect not seen fasted or with carbs only. In this context, lower cortisol could boost metabolic activity of muscle protein synthesis by allowing it to go on unscathed (cortisol increase protein breakdown and decrease synthesis).

In short, you have everything to gain by ingesting protein shortly prior to your “fasted” training session. The argument that pre-workout protein would interfere with fat burning can be laid to rest once and for all. Pre-workout protein will not only lead to better muscle and strength gains, but also help with fat loss due to it’s effects on metabolic rate.

Alternatively, ingest 30 g of whey protein 5-15 mins prior to training. This will yield similar amounts of BCAA as the above protocol.

Break the fast post-workout. Your 8 hour feeding window starts here.

Ideally, break the fast with your largest meal and taper caloric content of meals downwards throughout the day. End the 8-hour feeding window with a lower carb meal containing slow digesting protein such as cottage cheese or eggs. Meat served with fibrous veggies is another option (meat is a fairly “fast” protein, but fiber will slow digestion).

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Martin Berkhan

My name is Martin Berkhan and I work as a nutritional consultant, magazine writer and personal trainer.